free memory in Linux

I did free -tm on my system, and I got the output below.

Is the free buffers/cache part of the used memory? And therefore we can consider it as free memory?

             total       used       free     shared    buffers     cached
Mem:          5721       5689         32          0        137       4664
-/+ buffers/cache:        887       4834
Swap:         6000         13       5987

Total:       11722       5703       6019

Thanks

Answer

take a look at this post here on serverfault. it will explain the free output to you.